The present invention relates to occupancy sensors.
An occupancy sensor is an energy conservation device designed to detect the presence of human occupant(s) in a given area. When occupancy is sensed, the various electrically-powered loads in that area controlled by the sensor (for example, lights, ventilation, and the like) are energized. When that same area has been unoccupied for a predetermined period of time, the sensor de-energizes the electrical loads that it controls. Occupancy sensors may therefore conserve a great deal of energy in areas where the occupants do not exercise diligence in de-energizing those electrical loads when they leave the area.
Over the last few decades, several events have led to the growth of a large consumer market for energy saving devices including occupancy sensors. First, there has been an increase in public awareness of energy conservation and its beneficial environmental consequences. In addition, there has been increased realization by both private and government-controlled power generation industries of the economic and environmental advantages of energy conservation as a means of meeting peak load power demands. Finally, there have been legislative mandates at the federal, state and local levels for the use of energy conserving devices, such as occupancy sensors, in government and other public buildings.
Significant innovation in the design of occupancy sensors has occurred over the last few decades. The early occupancy sensors utilized primarily analog signal processing techniques, and typically employed a single type of sensing technology, such as ultrasonic, passive infrared, pressure, microwave, photoelectric, or audible sound. These single technology occupancy sensors were subject to false tripping due to a variety of reasons. For example, ultrasonic Doppler sensors were subject to false trips due to air conditioning and heating system air flow. In addition, since these sensors had no means of range discrimination, they were subject to false trips due to motion outside the desired range of interest. Similarly, passive infrared (PIR) sensors were subject to being blinded by intense, stationary sources of infrared energy.
The next generation of occupancy sensors used two or more sensing technologies. These sensors typically required the user to specify a separate activation threshold for each detector technology in the sensor. The digital detector output of each sensor technology was then combined using classical digital logic to detect occupancy. In general, these multiple sensing technology sensors had better performance than their predecessors but still exhibited a sensitivity-false alarm tradeoff.
In general, prior art occupancy sensors heretofore known suffer from a number of disadvantages relating to the ability to use such sensors in different environments and different commercial applications. In particular, these sensors suffer from the inability to provide broad coverage of large areas without resorting to multiple sensors pointing in multiple directions, the lack of a simple installation and removal mounting scheme, and the inability to selectively mask a sensor to accommodate different operating environments while maintaining simple installation and adjustment.